@article{MZM_1993_54_5_a4,
     author = {A. A. Zenkin},
     title = {Waring's problem for sums of fourth powers of positive integers: $g(1,4)=21$},
     journal = {Matemati\v{c}eskie zametki},
     pages = {45--52},
     publisher = {mathdoc},
     volume = {54},
     number = {5},
     year = {1993},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1993_54_5_a4/}
}